The Flora of Svalbard

Sexual reproduction by seeds is not proven but may perhaps happen now and then (see comments). The species produces large amounts of bulbils which fall to the ground. They may also be eaten by, e.g., reindeer or ptarmigan and thereby spread over longer distance. Tests have shown that ca 70% of the bulbils sprout after one year cold storage (Alsos et al. in prep.). Bulbils have also sprouted from seed bank (Cooper et al. 2004). Thus, although they are more fragile than seeds, they may provide an efficient way of spread and recruitment, and due to their construction, they furnish the emerging new plant with more nutrients than a seed normally receives from its endosperm.

The two Saxifragas in Svalbard with bulbils − S. cernua and S. svalbardensis − both differ from Micranthes foliolosa by having leafy flowering stems. None of the other species of Micranthes have bulbils. The only generally similar species in northern Europe is M. stellaris (Scandinavia, Iceland, and farther south), differing in having normal flowers and absence of bulbils, and also in a different leaf shape.

Of the four species of Micranthes in Svalbard, M. foliolosa and M. hieraciifolia are easily separable even on their leaves. Micranthes foliolosa has characteristic, obovate or obcuneate leaves with a few triangular teeth in the distal 1/3 only, and the leaves are thin and glabrous; M. hieraciifolia has ovate or lanceolate, subacute or acute leaves with sparse, shallow teeth along the sides, and the leaves are thick and with white, multicellular hairs along the margins and on the lower surface. Micranthes nivalis and M. tenuis both have thick, rounded leaves with obtuse, forward pointing teeth, and they are not easily separable on their leaves alone. However, whereas M. nivalis has a fair amount of white and often some brown hairs along the leaf margins and on the lower surface, M. tenuis has only a scattering of very dark brown hairs on the lower surface.

Not thermophilous. Most often observed in wet places such as shallow marshes, open patches with little vegetation in moist or wet tundras, moist snowbeds, or moist to wet patterned ground. In fine textured soils with acidic to basic soil reaction, but less frequent in strongly acidic substrates. Requires a moderate to good protection of snow during winter, and with the bulbils adapted to a short growth season. Probably little grazed by reindeer or geese.

Micranthes foliolosa is a circumarctic species, mainly octoploid (2n = 56), and belongs in a group together with the mainly tetraploid (2n = 28), amphi-Atlantic M. stellaris, the mainly tetraploid (2n = 20) NE Asian M. redofskyi, and the tetraploid and higher polyploid (2n = 20 and 38) American Beringian M. ferruginea. An origin of the bulbil-reproducing M. foliolosa from the seed-reproducing M. stellaris has been suggested, but this is a provincial European viewpoint. Morphological features and molecular evidence (A. Tribsch pers. comm.) both suggest a much closer relationship with the NE Asian M. redofskyi, possibly in combination with the Beringian M. ferruginea. (Hultén 1968) described a Saxifraga (Micranthes) foliolosa var. multiflora from W Alaska, characterized vs. M. foliolosa s. str. by presence of multiple flowers besides bulbils. Multi-flowered M. foliolosa is frequent on both sides of the Bering Strait as are plants with lower chromosome numbers (2n = 40, 48) than typical of M. foliolosa. These plants are intermediate between M. foliolosa and M. redovskyi. It is distinctly suggested that M. foliolosa has a hybrid origin, that its place of origin and its parents are found in Beringia, not in European M. stellaris (see Elven et al. 2011), and that the transition to bulbil reproduction has been successful as M. foliolosa is much more widespread (circumpolar) than any of its suspected parental relatives.

Alsos, I.G., Müller, E. & Eidesen, P.B. In prep. Germinability of 87 arctic species stored in Svalbard Global Seed Vault.

Cooper, E.J., Alsos, I.G., Hagen, D., Smith, F.M., Coulson, S.J. & Hodkinson, I.D. 2004. Recruitment in the Arctic: diversity and importance of the seed bank. – Journal of Vegetation Science 15: 115–124.

Elven, R., Murray, D.F., Razzhivin, V. & Yurtsev, B.A. 2011. Annotated Checklist of the Panarctic Flora (PAF). – Oslo: CAFF/University of Oslo.

Hultén, E. 1968. Flora of Alaska and Yukon. – Arkiv för Botanik, ser. 2, 7, 1. 147 pp.